Jump to content

Non-Newtonian fluids for battery safety


Recommended Posts

A recent article on Fireproof Lithium-Ion Batteries That Harden When Hit opens the possibility that the same engineering principles that protect our extremities from impact may improve battery safety... However, there could be some trade-offs in overall capacity and a potential price premium. Still, these will probably be on the market sooner than solid-state batteries because they are essentially 'drop-in' components to today's tech.

Considering how much we already spend on protective wear, shouldn't we prioritize incorporating this technology for our vehicle's safety?

  • Upvote 1
Link to comment
Share on other sites

Not a bad idea, but I don't think that batteries getting crushed or pierced is a common occurrence with EUCs, electric cars moving at 100km/h and hitting a solid obstacle is a different issue (for example Teslas have the undercarriage of the car filled with battery cells, hard hit there will rupture/crush the cells and cause a fire). For wheels, the most common issue seems to be short circuiting the battery through the motor, mainboard or wiring, and for that, this won't do anything. 

There are safer lithium-chemistries, like LiFePo (lithium iron phosphate) and LTO (lithium titanate). Both are much safer and don't ignite as easily (if at all, I think at least some LiFePos or was it LTOs can withstand full short circuit, the cell will heat up but won't catch fire or explode). The typical downsides are that they're lower nominal voltage chemistries, which makes them lower capacity => more cells in series are needed for high voltages and more packs in parallel for high capacities, making the battery packs larger, heavier and more expensive.

Quote

A lithium–titanate battery is a modified lithium-ion battery that uses lithium-titanate nanocrystals, instead of carbon, on the surface of its anode. This gives the anode a surface area of about 100 square meters per gram, compared with 3 square meters per gram for carbon, allowing electrons to enter and leave the anode quickly. This makes fast recharging possible and provides high currents when needed.[6] Lithium Titanate cells also last 3000-7000 charge cycles, far longer than other battery chemistries.[7]

A disadvantage of lithium-titanate batteries is that they have a lower inherent voltage (2.4 V), which leads to a lower specific energy of about 30–110 Wh/kg[8] than conventional lithium-ion battery technologies (which have an inherent voltage of 3.7 V).[9]

 

Quote

The LiFePO4 battery uses a lithium-ion-derived chemistry and shares many advantages and disadvantages with other lithium-ion battery chemistries. However, there are significant differences.

LFP chemistry offers a longer cycle life than other lithium-ion approaches.[13]

Like nickel-based rechargeable batteries (and unlike other lithium ion batteries),[14] LiFePO4 batteries have a very constant discharge voltage. Voltage stays close to 3.2 V during discharge until the cell is exhausted. This allows the cell to deliver virtually full power until it is discharged, and it can greatly simplify or even eliminate the need for voltage regulation circuitry.

Because of the nominal 3.2 V output, four cells can be placed in series for a nominal voltage of 12.8 V. This comes close to the nominal voltage of six-cell lead-acid batteries. And, along with the good safety characteristics of LFP batteries, this makes LFP a good potential replacement for lead-acid batteries in many applications such as automotive and solar applications, provided the charging systems are adapted not to damage the LFP cells through excessive charging voltages (beyond 3.6 volts DC per cell while under charge), temperature-based voltage compensation, equalisation attempts or continuous trickle charging. The LFP cells must be at least balanced initially before the pack is assembled and a protection system also needs to be implemented to ensure no cell can be discharged below a voltage of 2.5 V or severe damage will occur in most instances.

The use of phosphates avoids cobalt's cost and environmental concerns, particularly concerns about cobalt entering the environment through improper disposal,[13] as well as the potential for the thermal runaway characteristic of cobalt-content rechargeable lithium cells manifesting itself.

LiFePO4 has higher current or peak-power ratings than LiCoO2.[15] The energy density (energy/volume) of a new LFP battery is some 14% lower than that of a new LiCoO2 battery.[16] Also, many brands of LFPs, as well as cells within a given brand of LFP batteries, have a lower discharge rate than lead-acid or LiCoO2.[citation needed]Since discharge rate is a percentage of battery capacity a higher rate can be achieved by using a larger battery (more ampere hours) if low-current batteries must be used. Better yet, a high current LFP cell (which will have a higher discharge rate than a lead acid or LiCoO2 battery of the same capacity) can be used.

LiFePO4 cells experience a slower rate of capacity loss (aka greater calendar-life) than lithium-ion battery chemistries such as LiCoO2 cobalt or LiMn
2O4
 manganese spinel lithium-ion polymer batteries (LiPo battery) or lithium-ion batteries.[17] After one year on the shelf, a LiFePO4 cell typically has approximately the same energy density as a LiCoO2 Li-ion cell, because of LFP's slower decline of energy density.[citation needed]

 

Edited by esaj
Link to comment
Share on other sites

11 hours ago, esaj said:

The typical downsides are that they're lower nominal voltage chemistries, which makes them lower capacity => more cells in series are needed for high voltages and more packs in parallel for high capacities, making the battery packs larger, heavier and more expensive.

I guess a 'better' battery for our needs would require more energy density at lower cost. IMO, changes are just over the horizon (4 batteries).

So much going on in the battery market these days... With so many promising new lithium-chemistries in the pipeline, big investments in production facilities are happening now. LG Chem and Samsung SDI are losing market shares to competitors from China; meanwhile, CATL and BYD are making huuuge investments in production to meet Chinese EV demands.

Additional facilities are being built all over Europe (expected to be the next big EV market). The Swedes, Germans, and Chinese are all making large investments in new factories and the Koreans appear to be following suit (LG Chem, Samsung SDI, and SK Innovation have announced plans). That leaves Panasonic relying on it's partnership with Tesla and the US EV market coming to fruition. While impressive, the Gigafactory is going to have a lot of competition in the next few years...

Hopefully, all the competition will benefit EUC's... (Unless EV's become so popular, battery suppliers cannot meet other demands.)

Edited by RayRay
safer batteries couldn't hurt either...
  • Upvote 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...